232 



MANUAL OF THE MOLLUSCA. 



that he has found traces of very slender spiral lamellae occupying the furrows. 



This curious little shell most resembles the Triassic Leptana dubia (Pro 



ducta) Minister (= Crania Murc/dsoni, Klipst. !) 

 DAVIDSONIA, Bouchard. 

 Dedicated to the author of the Monograph of British Fossil Brachiopoda 

 Type, D. Verneuili, Bouch. Fig. 151. Devonian, Eifel. 



Fig. 151. Dorsal valve. 



Ventral valve, 



Shell solid, attached by outer surface of the ventral valve to rocks, shells, 

 and corals ; valves plain, articulated ; ventral valve with a wide area (K) ; 

 foramen angular, covered by a convex deltidium (d] : disk occupied by two < 

 nical elevations, obscurely grooved by a spiral furrow of 5-6 volutions ; dorsa 

 valve with two shallow lateral cavities ; vascular impressions consisting of 

 two principal sub -marginal trunks, in each valve, with diverging branches ; 

 cardinal and adductor impressions distinct. The furrowed cones undoubtedly 

 indicate the existence of spiral arms, similar to those of Atrypa (fig. 144), 

 but destitute of calcified supports. The mantle-lobes seem to have conti- 

 nued depositing shell until the internal cavity was reduced to the smallest 

 possible limit. 



Fig. 152. Dorsal valve. Ventral valve. 



? CALCEOLA, Lamarck. 



Etf/m. Calceola, a slipper. Type, C. sandalina, PL XV. fig. 26. Fig. 152. 

 Shell thick, triangular ; valves plain, not articulated : ventral valve pyra- 

 midal ; area large, flat, triangular, with an obscure central line ; hinge-lin? 

 straight, crenulated, dorsal valve flat, semi-circular, with a narrow area (h), 

 a small cardinal process (j), and two lateral groups of small apophysary (?) 

 ridges (b) ; internal surface punctate-striate. Fossil, Devonian, Eifel, Brit. 



